1. Field of the Invention
The present invention relates to an apparatus for manufacturing granules including a spray nozzle disposed within a granulating chamber of an apparatus body for feeding by spraying into the granulating chamber a liquid material comprising at least one of mixture having solid and liquid in a mixed state and solution including solid dissolved therein, an air blowoff portion provided at a lower region of the granulating chamber for feeding air for floating and fluidizing the liquid material and fine particles under granulation inside the granulating chamber, and an air exhaust port provided at an upper region of the granulating chamber for exhausting the air present inside the granulating chamber. The invention relates also a method of manufacturing granules.
2. Description of the Prior Art
In the discussion to follow, the term xe2x80x9cgranulesxe2x80x9d refer to material obtained from fine primary particles by spraying the liquid material to them so that the particles have obtained somewhat increased diameter. The granules may be formed solid or may include a number of voids therein. Also, an aggregate of a plurality of such granules will be referred to hereinafter as a granular element. This granular element may be such that the individual granules are separated to be movable relative to each other or may be also a single agglomeration thereof.
Further, the term xe2x80x9cprimary particlesxe2x80x9d refer to seed particles for forming the granules. For instance, as described later herein, they refer to fine particles or the like which are formed when the sprayed liquid material is dried and solidified immediately after being sprayed from the spray nozzle.
An example of conventional granule manufacturing apparatus is disclosed in Japanese patent application xe2x80x9cKokaixe2x80x9d No. Hei. 09-103668.
According to this apparatus, raw material particles serving as seeds for manufacturing granules are stored or charged in advance inside the granulating chamber. These raw material particles are fluidized by means of fluidizing air so as to form a fluidizing layer at a lower region of the granulating chamber Then, liquid material for granulation is sprayed downwardly and laterally from upper and lateral positions of this fluidizing layer to grow the raw material particles.
Specifically, as shown in FIG. 22, the raw material particles are stored at the bottom of the granulating chamber 1. At this bottom, there is mounted a rotor 42 rotatable about a vertical shaft 44. The rotor 42 defines a number of vent holes, through which fluidizing air 6 is supplied from under the rotor 42 to form an upwardly oriented air current inside the granulating chamber 1, whereby the fluidizing layer R is formed immediately above the rotor 42. To this fluidizing layer R, the liquid material 3 is sprayed from spray nozzles 4 disposed upwardly and laterally of the fluidizing layer R in directions opposed to and transverse the flow of the fluidizing air 6, so as to grow the raw material particles to manufacture the granules.
However, when this conventional manufacturing apparatus is employed for manufacturing spherical and heavy granules with sharp size distribution, the following problems exist.
Namely, with the conventional manufacturing apparatus, it is necessary to prepare the raw material particles in advance inside the granulating chamber. In order to charge them into the granulating chamber to use them as raw material particles, certain conditions need to be satisfied, such as the particles should not be coagulated easily and the size distribution should be uniform. For this reason, the preparation of the raw material would tend to be troublesome, imposing a certain limit in improving the manufacturing efficiency of the granules.
Further, with the conventional manufacturing apparatus, the spray nozzle 4 for downwardly spraying the liquid material 3 is disposed at an upper position inside the granulating chamber 1. And, this spray nozzle 4 sprays the liquid material 3 in the direction opposing the air 6 blown upward from the lower region of the granulating chamber 1. The liquid material 3, which is formed into fine droplets (mist) as the result of spraying, adheres to the raw material particles inside the fluidizing layer R to grow these raw material particles. However, in order to ensure that the downwardly sprayed liquid material 3 reaches the fluidizing layer R, it is necessary to limit the momentum of the upwardly directed air 6 to a certain extent. As a result, the space between the raw material particles inside the fluidizing layer R becomes insufficient, thus tending to invite coagulation of the raw material particles. For this reason, the granules obtained by using the conventional manufacturing apparatus tend to have a wide size distribution.
Moreover, the granules obtained by the above-described process tend to have a structure with many voids. Hence, it was difficult to obtain heavy granules.
Incidentally, another type of conventional apparatus includes a mechanism for intermittently blowing high-pressure air against the fluidizing layer R. For instance, the apparatus includes a plurality of jet nozzles 46 mounted along the periphery of the apparatus body 2 for discharging the air or gas against the fluidizing layer R. And, these respective nozzles 46 are mounted so that the gas discharging directions from all the nozzles will be focused at a single point within the fluidizing layer R.
Then, the particles inside the fluidizing layer R will blown by the high-pressure air currents toward the center of the granulating chamber 1 to collide against each other. This collision adds to the pulverizing effect of the counter jet mill, so that the granules tending to coagulate will be pulverized or cracked (hereinafter, xe2x80x9ccrushedxe2x80x9d). Consequently, it becomes possible to render the particle diameters of the resultant granules uniform.
However, with the conventional manufacturing apparatus, the granules under granulation would coagulate easily. Hence, it was difficult to allow the above-described crushing effect to manifest itself effectively.
The present invention is intended to solve the above-described drawbacks of the conventional art and to provide a granule manufacturing apparatus and method capable of manufacturing spherical and heavy granules of a desired particle diameter in an efficient manner.
The characterizing features of the granule manufacturing apparatus and method relating to the present invention are as follows.
The granule manufacturing apparatus according to the present invention, as shown in FIG. 1, is characterized in that the spray nozzle is designed to spray the liquid material upwardly, the granulating chamber includes a cylindrical wall portion and a generally conical wall portion; the spray nozzle is disposed at a lower center region of the granulating chamber; the cylindrical wall portion is provided at a portion beside the nozzle; the nozzle includes a spraying opening which is located at a top or inwardly of a conical plane including the wall portion; and a bag filter is disposed between the spray nozzle and the air exhaust port, the bag filter having a backwashing unit, the bag filter providing the function of sweep-off means for sweeping off solids collected on the bag filter as well as the function of pressure applying means for momentarily increasing the pressure inside the granulating chamber.
If the liquid material is sprayed upward as proposed by the above construction, the spraying direction and the air supplying direction agree to each other. So that the spraying of the liquid material will proceed smoothly to ensure a sufficient floating period for the spray droplets of the liquid material. Thus, these spray droplets will be solidified completely to be formed into primary particles without coagulation with other primary particles. The effect of prevention of coagulation can be provided also during the subsequent process of the primary particles growing into the granules.
If no coagulation of granules occurs during granulation as described above, the granules will not combine each other to form granules of an excessively large particle diameter. And, the growth of the granules during granulation process will proceed in a continues manner, so that granules with reduced particle size difference may be obtained. For instance, if granules having a narrower size distribution are obtained as above, then, such additional device as a classifier, which is needed by the standard manufacturing apparatus, would be omitted. Therefore, it becomes possible also to form the manufacturing apparatus compact.
Also, if the spray nozzle is disposed at a lower region of the granulating chamber, it is possible to secure a large space in the spraying direction of the liquid material. Hence, it is possible to restrict mutual coagulation of the granules during the manufacture and also to extend the floating and flowing period of the sprayed droplets, thus allowing the liquid material to be dried and solidified reliably. And, if the nozzle is disposed at the center of the granulating chamber, it is possible to secure a substantially constant distance from the nozzle to any position of the cylindrical wall portion, thus helping to prevent adherence of the sprayed liquid material from to a specific portion of the cylindrical wall portion.
Normally, the liquid material sprayed and fed into the granulating chamber will be dispersed more as it floats and flows upwardly. Then, by providing the generally conical wall portion having a progressively increasing width upwardly, this serves to reduce the opportunity for the upwardly floating granules to adhere to the wall portion. As a result, mutual coagulation of granules may be further restricted and the floating period may be extended also, whereby the drying and solidifying process of the granules may proceed reliably.
And, in particular, if the cylindrical wall portion is provided at a portion beside the nozzle and the nozzle includes a spraying opening which is located at a top or inwardly of a conical plane including the wall portion, dispersion of the liquid material sprayed from the spray nozzle may be restricted to some extent by the air. So that, it is possible to e.g. prevent adherence of the liquid material to the cylindrical wall portion, whereby the liquid material may be caused to float inside the granulating chamber in a reliable manner.
Moreover, with this construction, the spraying direction of the liquid material from the nozzle is caused to agree substantially with the extending direction of the wall portion, so that the possibility of adherence of the liquid material to the wall portion may be further reduced.
The granule manufacturing apparatus of the invention, as shown in FIG. 6, includes a bag filter having a backwashing unit is disposed at an upper portion of the granulating chamber and between the spray nozzle and the air exhaust port.
The spray droplets of the liquid material will float and flow inside the granulating chamber while being dried and solidified. Since the air inside the granulating chamber flows upward by the exhaustion through the air blowoff portion, the granules of the liquid material too will be gradually drawn to the upper region of the granulating chamber. The granules drawn upward will be collected by the bag filter. This bag filter serves to prevent the granules from being discharged to the outside of the apparatus body when the air in the granulating chamber is exhausted and the filter serves also as an area for allowing the granules to be dried. These collected granules will be dried substantially completely as they remain adhered to the bag filter. In these granules adhered to the bag filter, any moisture present therein has evaporated, so that coagulation of the granules due to the remaining moisture will hardly occur.
This bag filter functions as sweep-off means for sweeping off solids collected on the bag filter. The backwashing unit of the bag filter serves to momentarily cause the air to flow reversely through the filter inside the granulating chamber. The granules after completion of drying thereof by the bag filter will be caused to be dropped off the bag filter again into the granulating chamber by the backwashing unit. The sweeped-off granules will again float and flow inside the granulating chamber and the granules circulated to the vicinity of the spray nozzle will be sprayed again with liquid material from the spray nozzle. These granules coated with liquid material will be dried while floating and flowing inside the granulating chamber and be adsorbed by the bag filter. With repeated cycles of such growth process, granules having a desired particle diameter may be formed.
By using the bag filter having a backwashing unit as proposed by the above-described construction, granules having a predetermined particle diameter may be manufactured within a limited space, so that the entire manufacturing apparatus may be formed compact.
Further, with the granule manufacturing apparatus of the invention, the bag filter functions also as pressure applying means. With this construction, it is possible to momentarily increase the pressure inside the granulating chamber momentarily, thus applying momentary external impact to the periphery of the granule in the course of manufacture thereof As a result, the granules will grow while being compacted at the same time, whereby heavy granules having high strength may be obtained.
As described above, through the effective utilization of the backwashing unit both as the sweep-off means and as the pressure-applying means, it is possible to obtain granules which are heavy, spherical and have high strength. Also, the construction of the manufacturing apparatus may be simplified.
The granule manufacturing apparatus, as shown in FIG. 14, is characterized in that the granulating chamber includes a jet nozzle for jetting high-pressure gas against the fluidizing layer.
With this construction, the granules which have become larger as a result of coagulation in the granulation process may be crushed into a suitable size by means of the high pressure air. Hence, granules having a very narrow size distribution may be obtained. Moreover, by adjusting the strength of the high pressure air, it becomes also possible to set the size of the granules as desired.
The granule manufacturing apparatus, as shown in FIG. 21, is characterized in that the apparatus further comprises a downwardly directed spray nozzle disposed at an upper region inside the granulating chamber for downwardly spraying the liquid material inside the granulating chamber.
According to the manufacturing apparatus having the above construction, the spraying operation of the liquid material inside the granulating chamber is effected by means of the upwardly directed spray nozzle disposed at a lower region of the granulating chamber as well as said downwardly directed spray nozzle. With this construction, the liquid material may be sprayed over a wider area of the granulating chamber. Especially, in order to improve the granulating efficiency when a liquid material having a high drying speed is employed, it is preferred that the liquid material be sprayed by short time intervals. Then, according to this construction, the liquid material is sprayed to nearly all positions inside the granulating chamber. With this, additional liquid material may be caused to adhere to the granulate present at nearly every position during the manufacture process.
The granule manufacturing apparatus, as shown in FIG. 21, is characterized in that the apparatus further comprises a horizontally directed spray nozzle attached to the wall of the granulating chamber for laterally spraying the liquid material relative to the fluidizing air current inside the granulating chamber.
In this case too, by providing the horizontally oriented spray nozzle, the liquid material may be sprayed over a wider area of the granulating chamber. As a result, the amount of the liquid material adhered to each granulate during the manufacture thereof may be rendered uniform, so that the thickness of the liquid film formed on the surface of each granule may be uniform as well. There will occur no sudden growth of granules, and the adhesion and drying cycles of the liquid material may be repeated reliably. Accordingly, no porous structure will be formed and uniform, dense and heavy granules may be obtained.
The granule manufacturing apparatus, as shown in FIG. 13, is characterized in that the bottom of the granulating chamber is constructed of a rotor in the form of a generally circular disc.
By providing a rotor at the bottom of the granulating chamber as proposed by the above construction, one can expect a compacting effect due to the rolling in addition to the compacting effect from the pressure applying means, whereby even heavier and stronger granules may be obtained.
Further, as the granules are caused to roll by the rotor, globurizing of the granules may be further promoted.
Moreover, by providing the rotor, it is possible to manufacture larger granules which can not be blown upward by the air from the air blowoff portion. That is, such large granules will be accumulated on the rotor. But, as this rotor is being rotated, the granules thereon too will roll incessantly, so that the liquid material sprayed from the nozzle may be caused to adhere to the surfaces of the granules uniformly.
The granule manufacturing apparatus, as shown in FIG. 6 and FIG. 8, is characterized in that a jacket for circulating fluid is provided over substantially entire outer periphery of the spray nozzle for optimizing the temperature of the liquid material to be sprayed and supplied, the spray nozzle includes a needle at a liquid spray opening thereof for spraying the liquid material, with a needle being shiftable between an opening position for opening the spray opening for the liquid material and a closing position for closing the spray opening for the liquid material; and when the needle closes the liquid spray opening, the leading end of the needle projects from the liquid spray opening, so that even if solidification of the liquid material tends to occur at the liquid spray opening, the solidified material may be eliminated by the needle, whereby the liquid spray opening may be maintained under a clean condition.
If the jacket is provided over the substantially entire outer periphery of the spray nozzle for optimizing the temperature of the liquid material to be sprayed and supplied as proposed by the above-described construction, it becomes possible to prevent solidification/deterioration of the liquid material within the spray nozzle, so that continuous operation of the manufacturing apparatus becomes readily possible.
Further, by optimizing the temperature of the liquid material, the viscosity of the liquid material may be made suitable for its spraying. Accordingly, e.g. the particle diameter of the sprayed droplets may be rendered uniform and the growth speed of the granules may be rendered constant, whereby quality granules with uniform particle size may be obtained.
Moreover, as shown in FIG. 8, if the spray nozzle includes a needle at a spray opening thereof for spraying the liquid material, with the needle being shiftable between an opening position for opening the spray opening for the liquid material (xe2x80x9cliquid spray openingxe2x80x9d hereinafter) and a dosing position for closing the spray opening for the liquid material, the following effects can be achieved.
This liquid spray opening is exposed inside the granulating chamber, thus exposed to the fluidizing air. Therefore, of the liquid material present within the spray nozzle, especially a portion thereof present adjacent the liquid spray opening tends to be dried and solidified more easily. If it is solidified, this will lead to abnormality in the opening area or shape of the liquid spray opening, thus resulting in change in the spraying condition of the liquid material, consequently, non-uniformity in the particle diameter of the sprayed droplets. As a result, it becomes difficult to obtain granules of uniform particle size.
With the above-described construction including the needle shiftable at the liquid material spraying opening with the leading end of the needle projecting from the liquid spray opening when the needle closes the liquid spray opening, even if solidification of the liquid material tends to occur at the liquid spray opening, the solidified material may be eliminated by the needle. Accordingly, the liquid spray opening may be maintained under a dean condition. As a result, the manufacturing apparatus may be operated continuously for a longer period of time, whereby the manufacturing efficiency of the granules may be further improved.
The granule manufacturing apparatus, as shown in FIG. 6, is characterized in that the spray nozzle is disposed at a lower region inside the granulating chamber for upwardly spraying the liquid material.
Especially, when the manufacture is to be started from a condition where no raw material particles are charged at all in advance into the granulating chamber, it is important to control the temperature, viscosity, etc. of the liquid material. In particular, at the initial stage of the granulation, the sprayed droplets of the liquid material are very small. Therefore, it is important to control the spraying condition in order to e.g. prevent mutual coagulation of the particles.
Then, if the spray nozzle having the jacket is directed upwards, it becomes possible to optimize the spraying condition of the liquid material at this initial stage of granulation, so that the liquid material may be dispersed sufficiently inside the granulating chamber. Consequently, the granulating efficiency may be improved significantly and granules having narrow size distribution may be manufactured.
According to a method of manufacturing granules, as shown in FIG. 1, for manufacturing granules using a spray nozzle for spraying liquid material upwardly, first, the manufacturing apparatus is constructed such that the granulating chamber includes a cylindrical wall portion and a generally conical wall portion, the spray nozzle is disposed at a lower center region of the granulating chamber, the cylindrical wall portion is provided at a portion beside the nozzle, and also that the nozzle includes a spraying opening which is located at a top or inwardly of a conical plane including the wall portion and a bag filter is disposed between the spray nozzle and the air exhaust port. Then, the method comprises the steps of: discharging a predetermined amount of the air from the air blowoff portion without charging any raw material particles into the granulating chamber; spraying/supplying the liquid material from the spray nozzle into the current of said air; causing sprayed droplets of the liquid material to float and flow inside the granulating chamber to form a group of particles; and spraying/supplying additional liquid material from the spray nozzle to the group of floating and flowing particles for growing the particles into granules, wherein said respective steps are effected while the backwashing unit is operated for sweeping off the solids collected on the bag filter and momentarily increasing the pressure inside the granulating chamber so as to compact the solids.
As proposed by the above construction, if the liquid material is sprayed and supplied to the current of air discharged upward for manufacturing granules, at the initial stage of the granulation, the primary particles formed of the sprayed and supplied liquid material may be caused to float and flow incessantly inside the granulating chamber, thus allowing the primary particles to grow without mutual coagulation thereof Thus, a group of fine particles are formed and consequently granules having a desired particle diameter and also minimized particle diameter variation may be obtained.
Further, with this construction, there is no need for charging raw material particles into the granulating chamber at the start of the granulation. As the granules can be manufactured only by spraying the liquid material, the manufacture efficiency of granules may be improved significantly.
Moreover, as described hereinbefore in the disclosure of the granule manufacturing apparatus relating to the present invention, especially if the spray nozzle is disposed at a lower center region of the granulating chamber, the cylindrical wall portion is provided at a portion beside the nozzle, and also the nozzle includes a spraying opening which is located at a top or inwardly of a conical plane including the wall portion, it is possible to secure a substantially constant distance from the nozzle to any position of the cylindrical wall portion, thus helping to prevent adherence of the sprayed liquid material to a specific portion of the cylindrical wall portion.
And, dispersion of the liquid material sprayed from the spray nozzle may be restricted to some extent by the air. So that, it is possible to e.g. prevent adherence of the liquid material to the cylindrical wall portion, whereby the liquid material may be caused to float inside the granulating chamber in a reliable manner.
Moreover, with this construction, the spraying direction of the liquid material from the nozzle is caused to agree substantially with the extending direction of the wall portion, so that the possibility of adherence of the liquid material to the wall portion may be further reduced.
In addition, by using the bag filter having a backwashing unit as proposed by this construction, like the above-described granule manufacturing apparatus, granules having a predetermined particle diameter may be manufactured within a limited space, so that the entire manufacturing apparatus may be formed compact.
According to a granule manufacturing apparatus, as shown in FIG. 17, the apparatus includes: a spray nozzle disposed within a granulating chamber of an apparatus body for feeding by spraying into the granulating chamber a liquid material comprising at least one of mixture having solid and liquid in a mixed state and solution including solid dissolved therein; an air blowoff portion provided at a lower region of the granulating chamber for feeding air for floating and fluidizing the liquid material and fine particles under granulation inside the granulating chamber; and an air exhaust port provided at an upper region of the granulating chamber for exhausting the air present inside the granulating chamber; the spray nozzle being disposed at a lower center region of the granulating chamber so as to spray the liquid material upwardly;
wherein a bag filter is disposed between the spray nozzle and the air exhaust port, the bag filter having a backwashing unit, the bag filter providing the function of sweep-off means sweeping off solids collected on the bag filter as well as the function of pressure applying means for momentarily increasing the pressure inside the granulating chamber; and
the granulating chamber contains a plurality of jet nozzles for jetting high-pressure gas against a fluidizing layer formed in the lower region of the granulating chamber, the jetting direction of the respective jet nozzles being oriented toward the center of the granulating chamber and with slight lower inclination.
With the granule manufacturing apparatus having this construction, since the spraying direction of the liquid material and the supplying direction of the air agree to each other in the upward direction, it is possible to assure the floating period for the sprayed droplets of the liquid material, so that granules may be manufactured without mutual coagulation of the sprayed particles.
Further, with the provision of the bag filter having the backwashing unit, this filter serves to prevent the granules from being discharged to the outside of the apparatus body when the air in the granulating chamber is exhausted and the filter serves also as an area for allowing the granules to be dried. Moreover, with the backwashing unit of the bag filter, the particles adhering to the bag filter may be caused to be dropped off the bag filter again into the granulating chamber to allow continuation of the floating/fluidizing inside the granulating chamber. Further, as the bag filter functions also as the pressure applying means for momentarily increasing the pressure inside the granulating chamber, it is possible to allow the granules to grow while they are being compacted.
And, according to the manufacturing apparatus having this construction, the high pressure air is sprayed against the granules provided with the upward velocity with the fluidizing air, an even stronger impact may be applied to these granules. As a result, even such granules having a stronger mutual coagulating force can be manufactured with effectively restricting coagulation thereof.
Also, even those granules which were not directly crushed will be moved to the inner side of the apparatus body by means of the high pressure gases jetted from the plurality of positions, these granules are caused to collide strongly against each other in the vicinity of the center. Hence, while restricting the growth of granules within a predetermined range, it is possible to obtain granules having a desired particle size.
According to a granule manufacturing apparatus as shown in FIG. 18, in particular, the granulating chamber contains, at four positions about periphery thereof, jet nozzles for jetting high-pressure gas against a fluidizing layer formed in the lower region of the granulating chamber, adjacent two jet nozzles forming a group, the high-pressure airs jetted from this group of jet nozzles intersecting each other inside the fluidizing layer, an intersection point of the one group being different from an intersection point of the other group.
With the manufacturing apparatus having this construction, since the crushing of the granules takes place at a plurality of positions inside the fluidizing layer, it is possible to extend the area affected by the crushing force of the high pressure gas. In this case, however, the impact applied to the granules will be smaller. Still, for instance, when granules having not so strong coagulating force are to be manufactured, it can be more effective to extend the effective area of the impact force than to increase the impact force. With the manufacturing apparatus of this construction, it is possible to efficiently manufacture granules having not so strong coagulating force during the manufacture thereof.